1. Field of the Invention
The present invention relates generally to fluid reaction surfaces, and more specifically to a gas turbine blade with tip cooling.
2. Description of the Related Art including information disclosed under 37 CFR 1.97 and
A gas turbine engine includes a turbine section with a plurality of rotor blade stages. A compressor supplies compressed air to a combustor to produce a hot gas flow through the turbine resulting in the generation of mechanical power. The rotating blades of the turbine form a seal between the blade tips and the outer shroud wall of the turbine. Thus, a seal is formed between two relatively rotating members of the turbine.
Leakage across this seal reduces the engine efficiency. Also, the leakage is hot gas flowing between the tip and the shroud. This hot gas flow on the tip will cause heating of the blade tip resulting in excessive wear or damage to the tip and shroud.
Rubbing of the tip against the shroud is also a problem because of thermal expansion of the blade from the heat load and from the centrifugal force developed in the blade from the rotation thereof. Squealer tips have been developed to provide a tip seal and to limit the amount of blade material that can rub. Cooling of the squealer tip is necessary to prevent the tip from overheating. Leakage in to the squealer tip cavity of the hot gas flow will cause the balder tip region to overheat.
U.S. Pat. No. 4,247,254 issued to Zelahy on Jan. 27, 1981 entitled TURBOMACHINERY BLADE WITH IMPROVED TIP CAP discloses a squealer tip for a turbine blade with cooling holes on the tip cal to inject cooling air into the cavity formed within the sidewalls of the squealer tip.
U.S. Pat. No. 5,511,946 issued to Lee et al on Apr. 30, 1996 entitled COOLED AIRFOIL TIP CORNER discloses a blade with a tip corner on the trailing edge having cooling holes that cross each other for improved cooling of the tip.
U.S. Pat. No. 5,660,523 issued to Lee on Aug. 26, 1997 entitled TURBINE BLADE SQUEALER TIP PERIPHERY END WALL WITH COOLING PASSAGE ARRANGEMENT discloses a turbine blade squealer tip with a cooling passages that cross one another to provide a larger cooling surface area and thereby more effective convective cooling that do separate single holes. The crossing cooling holes also cause for a more turbulent flow within the holes.
U.S. Pat. No. 6,932,571 B2 issued to Cunha et al on Aug. 23, 2005 entitled MICROCIRCUIT COOLING FOR A TURBINE BLADE TIP discloses a turbine blade with a tip having a microcircuit that traverses the tip between a suction sidewall and a pressure sidewall.